LAUSR

BACKGROUND Immunization programs' resilience to shocks is central to their success, but little empirical evidence documents resilience in action. We sought to characterize the decline of HPV vaccination in Denmark after negative media coverage and recovery during a national information campaign. METHODS We conducted a population-based retrospective cohort study of all girls born in Denmark from 1997 to 2006 (N = 328,779), aged 12-15. The outcome measure was HPV vaccine uptake (first dose), as reported to the Danish national health registry from 2009 to 2019, when HPV vaccine was freely available to girls in primary care clinics in Denmark. Events that created 4 natural time periods for study were HPV vaccine reaching the uptake of other vaccines in the national program (2009), some negative media coverage of HPV vaccination (2013), extensive negative media coverage (2015), and a national information campaign about the vaccine's safety and effectiveness (2017-2019). RESULTS In the period with some negative media coverage, HPV vaccine uptake fell to 83.6% (95% CI:78.0%-89.7%) of baseline uptake. In the period with extensive negative media coverage, uptake fell even further to 49.6% (95% CI:44.5%-55.2%) of baseline uptake. After the information campaign, HPV vaccine uptake recovered to its baseline level (109.2%, 95% CI:90.1%-132.4%) due in part to catch-up doses. Despite the recovery, an estimated 26,000 fewer girls initiated the vaccine than if uptake had not declined. CONCLUSIONS The experience in Denmark offers one of the first opportunities to document how a nation grappled with negative media coverage of HPV vaccination and the steadying impact of action by national authorities.